The present invention relates generally to a tool for induction heating of components to be joined one to the other and particularly relates to an induction heating coil for brazing copper components at electrical generator locations difficult to access and braze by conventional brazing tools.
Brazing component parts together is an old and tried method of joining the parts. Typically, brazing is accomplished by using an open flame, for example, propane, and an oxygen gas in conjunction with brazing filler and flux materials. While such brazing method and tools are satisfactory for original equipment manufacture, oftentimes there is a need for brazing parts to one another in cramped and confined spaces where the use of an open flame cannot safely be utilized. For example, in a power generating facility, liquid cooled high voltage bushing components are located in the electrical generator lower frame extension. Field brazing of these components is oftentimes unacceptable in the power generating facility. Accordingly, there is a need for a brazing tool for induction heating of the parts to be brazed to one another which can be used in cramped, confined spaces, reused for multiple applications, and used for original equipment as well as field repair applications.
In accordance with a preferred embodiment of the present invention, there is provided a tool for brazing application including an induction coil formed of a pair of induction coil components which are substantially similar to one another, i.e., substantially mirror images of one another. Each component includes a linear extension or leg, whose proximal end is coupled to a first end of a generally semi-circular induction coil portion. The opposite or second end of the semi-circular induction coil portion terminates in a flange such that the opposed induction coil components can be secured one to the other. The distal end of each extension has an adapter flange portion forming part of an adapter for securing the tool to an induction brazer for supplying electrical current and cooling water to the induction tool. In that manner, an induction coil extending a full 360xc2x0 is formed having a specific diameter designed for a close fit about and used to join components of a particular diameter. The linear extensions lie parallel to one another along their lengths and have electrical insulating material therebetween. The induction coil components are preferably formed of hollow, electrical conductive, e.g., copper. Preferably, the tubes are rectilinear in cross-section.
At the opposite end of the tool and adjacent the juncture of the second ends of the semi-circular coil portions, there are provided a pair of nipples, one on each coil portion end. A flexible conduit, e.g., a hose, is attached to the nipples, whereby water flowing through the linear extension and semi-circular portion on one side of the tool traverses the joint between the components for flow through the semi-circular coil portion and linear extension of the other side of the tool. Additionally, an electrically conductive material, for example, a braid, interconnects the nipples or opposite sides of the semi-circular coil portions to one another to ensure electrical conductivity between the two component halves.
With the foregoing arrangement of the tool, the semi-circular component portions can be disposed on opposite sides of the parts to be brazed to one another and bolted to one another about the parts and to the brazer. The diameter of the semi-circular portions closely approximates the diameter of the parts to be brazed whereby high coupling efficiency with minimum applied power is provided while reaching and holding the brazing temperature. With the semi-circular portions of the brazing tool about the parts, the temperature is raised to the brazing temperature and the filler material, e.g., about 80% copper, 15% silver and 5% phosphorus, is applied to the parts. Other brazing alloys may be used. A cooling medium, e.g., water, is simultaneously supplied from the brazer through the tool to cool the tool during brazing. After brazing, the components are separated from one another by detaching the bolted connections at the semi-circular component portion end, as well as at the adapter end. The brazing tool is then opened, e.g., in a clamshell manner, and removed from about the brazed parts for reuse and reapplication to other parts required to be brazed to one another. It will be appreciated that the brazing tool is thus compact and can be utilized in confined spaces, for example, to braze the generator high voltage bushings and component parts thereof as necessary in a generator. Applications of the tool hereof to braze other parts in other environments are also within the scope hereof.
In a preferred embodiment according to the present invention, there is provided an induction coil for brazing comprising a pair of induction coil components, each component including a generally semi-circular induction coil portion and a generally linear extension extending from a first end of the semi-circular induction coil portion, each coil portion and extension being formed of a hollow, electrical conductive material for flowing a cooling medium and conducting electricity between an end of the extension, along the extension, and through the semi-circular induction coil portion to a second end of the semi-circular induction coil portion opposite the first end, means for releasably securing the components to one another such that the semi-circular induction coil portions form a generally circular coil for surrounding workpieces to be brazed to one another and with the extensions in opposed registration with one another and a bypass conduit for hydraulically connecting the coil portions to one another adjacent the second end thereof.
In a further preferred embodiment according to the present invention, there is provided an induction coil for brazing comprising a pair of induction coil components, each component including a generally semi-circular induction coil portion and an extension extending from a first end of the semi-circular induction coil portion, each coil portion and extension being formed of a hollow, electrical conductive material for flowing a cooling medium and conducting electricity between an end of the extension, along the extension, and through the semi-circular induction coil portion to a second end of the semi-circular induction coil portion opposite the first end, the second ends of the semi-circular induction coil portions being closed, a releasable securing device for securing the components to one another adjacent the second ends thereof such that the semi-circular induction coil portions form a generally circular coil for surrounding workpieces to be brazed to one another and a bypass conduit for hydraulically connecting the coil portions to one another adjacent the second end thereof whereby the cooling medium may flow serially through one component and subsequently another component.